RGP materials enabled a major shift away from both traditional preformed fitting methods and from impression methods as mainstream Scleral lens clinical practice.

Corneal swelling studies and clinical experience gained so far, indicates that sealed scleral lens designs provide sufficient oxygenation to alleviate significant corneal hypoxia. This crucial development has transformed scleral lens practice. Air bubbles are largely excluded from the pre-corneal fluid reservoir, and its positive pressure is retained, thereby significantly reducing settling back and enabling controlled corneal clearance.

Complex and unpredictable fitting processes are now only necessary in a minority of cases encountered. Virtually any corneal topography can be easily fitted with sealed RGP Scleral lenses, provided that the Sclera is regular enough to be fitted with a preformed design. If this is not the case, an impression may have to be taken, from which a PMMA scleral lens can be made in the traditional way, or the final fitted PMMA scleral lens can be duplicated in an RGP material.However, it should be pointed out that this duplication exercise is a cumbersome manufacturing exercise compared to any other scleral lens manufacturing process.